In office chairs, it is typically necessary to provide a mechanism which allows the chair user to adjust the vertical or lateral position of the back of the chair back relative to the chair seat. Such a mechanism permits the chair user to customize the chair to accommodate the user's particular size and comfort choices.
In the past, vertical chair back adjusting mechanisms have comprised a slider mounted on a chair back. The slider slidably engages an arm extending upwards from the chair seat. In order to lock the chair back in a fixed position, such mechanisms have further employed a screw assembly extending from the slider. The screw assembly, is typically operable by a lever, knob or handle. The screw mechanism, when tightened, causes a friction fit between the chair back slider and the arm. These known mechanisms, however, are cumbersome as they require a chair user to utilize both hands to effectively adjust the chair back.
Devices allowing one handed vertical adjustment of a chair back relative to a chair seat are known. For example, U.S. Pat. No. 4,749,230 issued Jun. 7, 1988 and naming Tornero as inventor discloses a height adjusting device for a chair backrest employing guided slidably interlocking plates and a locking pin disposed in a slotted track. This device, however, relies on the free sliding of the locking pin and the force of gravity on this pin. Accordingly, as the mechanism becomes dirty and worn it often fails to operate smoothly.
Similarly, U.S. Pat. No. 4,639,039 issued Jan. 27, 1987 and naming Donovan as inventor discloses a height adjustment mechanism for a chair backrest. This mechanism, while effective, utilizes numerous parts, including a coiled torsion spring. It is accordingly somewhat cumbersome to manufacture and assemble.
The present invention attempts to overcome many of the disadvantages of the known devices.